Refer to FIG. 1. In a digital resistive touch panel, a spacer 1A separates two films 2A and 3A; X-axis electrodes 4 and Y-axis electrodes 5 are respectively arranged on the films 2A and 3A; a controller 6A connects the ends of the X-axis electrodes 4 and Y-axis electrodes 5. By pressing to allow the two films 2A and 3A to contact each other, the X-axis electrodes 4 and Y-axis electrodes 5 are short-circuited, whereby the controller 6A can detect the position where the user presses.
Refer to FIG. 2. In a four-wire analog resistive touch panel, a spacer 1B separates two films 2B and 3B; two conductive layers 7 and 8 are respectively coated on the two films 2B and 3B; conductive contact layers 9 are arranged on two edges of the conductive layers 7 and 8, and two terminals at the conductive contact layers 9 of the conductive layers 7 and 8 in different directions. The controller 6B supplies a voltage to one edge of the film 2B. When the user presses to allow the two films 2B and 3B to contact each other, the controller 6B detects the divided voltages of the other three terminals of the film 2B and the other three terminals of the film 3B and calculates the position where the user presses.
The above-mentioned digital resistive touch panel has the multi-touch function but cannot sense the dragging path, i.e. lacks the handwriting-recognition function. The above-mentioned analog resistive touch panel can sense the dragging path but lacks the multi-touch function. Thus, the user cannot have both functions when using only one of the above-mentioned touch panels.
A US publication No. 2007/0152982 entitled “Input Device Supporting Various Input Modes and Apparatus Using the Same” discloses a portable device with a touch panel that has a telephone number input mode and a handwriting input mode. In the telephone number input mode, point touch can be performed. In the handwriting input mode, drag path sensing can be performed to do handwriting. However, the point touch and the drag path sensing can only be undertaken in separate input modes, and they cannot be operated in the same input mode at the same time. Therefore, the prior art still has room to improve.